A navigation system performs travel guidance for enabling a user to easily and quickly reach the selected destination. A typical example is a vehicle navigation system where a user drives a car having a vehicle navigation system. Such a navigation system detects the position of the user or user's vehicle, reads out map data pertaining to an area at the current vehicle position from a data storage medium, for example, a CD-ROM (compact disc read-only memory), a DVD (digital versatile disc), or a hard disc. Alternatively, such map data can be provided to the user from a remote server through a communication network such as Internet. The navigation system displays a map image on a monitor screen while superimposing a mark representing the current location of the user on the map image.
When a destination is set, the navigation system starts a route guidance function for setting a guided route from the start point to the destination. To determine the guided route to the destination, the navigation system calculates and determines an optimum route to the destination based on various parameters. For example, the guided route is determined based on the shortest way to reach the destination, the route preferring freeways to surface roads, the least expensive way to the destination, or the route without using toll road, and the like.
During the route guidance, the navigation system reads the nodes data from the data storage medium such as DVD and successively stores the nodes data of road segments (expressed in longitude and latitude) constituting the guided route in a memory. In the actual traveling, the node series stored in the memory is searched for a portion of the guided route to be displayed in a map display area of the monitor screen, and the portion of the guided route is highlighted so as to be discriminable from other routes. When the vehicle is within a predetermined distance of an intersection it is approaching, an intersection guidance diagram (an enlarged or highlighted intersection diagram with an arrow indicating the direction in which the vehicle is to turn at the intersection) is displayed to inform a user of the desired one of roads or directions selectable at the intersection. Such route guidance by the navigation system is also given by voice instruction.
FIGS. 1A-1H show an example of overall procedure and screen display involved in the navigation system. FIG. 1A shows an example of locator map screen of the navigation system when the destination is not specified. Typically, the navigation system displays a street on which the vehicle (current vehicle position VP) is running on a map image and a name of the street. Other information such as a north pointer NP, a map scale and a current time may also be illustrated on the display screen. However, in this situation, the navigation system does not perform the route guidance function because the destination is not specified.
FIGS. 1B-1D show an example of process for specifying a destination in the navigation system. A main menu screen such as shown in FIG. 1B displays menu items including a “Destination” menu for entering the destination. When selecting “Destination”, the navigation system displays an “Find Destination by” screen as shown in FIG. 1C for specifying an input method for selecting the destination. The “Find Destination By” screen lists various methods for selecting the destination including “Address” for specifying the city and address of the destination, “Intersection” for specifying the names of two streets which intersect with one another, and “Point of Interest” (POI) for selecting the programmed destination based on the name, category or telephone number. Other methods in the “Find Destination by” screen include “Recent Route” for specifying the destination based on the recent history of destinations saved in the navigation system, and “Address Book” for selecting the address of the destination out of the prescribed address list stored in the system.
When selecting, for example, the “Point of Interest” method in FIG. 1C, the navigation system displays selection methods of point of interest (POI) either by “Place Name” or “Place Type” in FIG. 1D. The “Place Name” is to specify a name of POI, and the “Place Type” is to specify a category of POI. If the “Place Name” is selected in FIG. 1D, the navigation system shows an “Enter Place Name” screen such as shown in FIG. 1E. The screen of FIG. 1E is basically a keyboard for inputting the name in an input box on the monitor screen. The user inputs the name of the desired POI in the input box through the keyboard.
FIG. 1F shows a “Confirm Route” screen of the navigation system for confirming the destination. In this example, the “Confirm Route” screen lists the name, address and phone number of the destination (i.e., the POI specified by the user). If this is the correct destination, the user enters an “OK to Proceed” key to proceed to the next procedure.
In FIG. 1G, the navigation system calculates and determines a guided route to the destination, i.e., the selected POI. The navigation system determines a route to the destination based on, for example, the shortest way to reach the destination, the route using as much freeway as practical or the route without using toll road, and the like. In this example, the navigation system displays a progress scale of the calculation of the route.
After determining the guided route, the navigation system starts the route guidance as shown in FIG. 1H. Typically, the navigation system shows the intersection which is highlighted to show the next turn and a direction of the turn. Such route guidance by the navigation system is also given by voice instruction.
In the process of specifying the destination by the “Point of Interest (POI)” method described above, because the recent storage medium provides a large volume of data involved in this input method, it requires relatively many steps until finally selecting the destination. Further, when there are a large number of POIs in a relatively small area, too many POIs will be displayed, which makes it difficult for the user to find the desired one.
For example, when finding a POI through a category such as “restaurant” in a downtown area, many POI names will appear on the navigation display, requiring the user to scroll many pages of the screen and to see many POI names. In another example, when the user does not know the exact name of the POI, thus, only a portion of the name is input through the keyboard, the navigation system will detect a large number of POIs including the portion of that name. Thus, it takes a long time to find a correct POI name by scrolling many pages of the list, which may adversely affect the safe driving. Therefore, there is a need for a navigation system which can easily and quickly specify the destination through the “Point of Interest” method.